1. Field of the Invention
The present invention relates to a power supply device for vehicles, which is mounted on a vehicle, has an output unit connected to a motor which is rotated with a drive wheel, supplies drive power to the motor during a power running operation of the motor, and recovers regenerative power of the motor during a regenerative operation of the motor.
2. Description of the Related Art
Conventionally, a power supply device for vehicles, in which a fuel cell and a capacitor are connected in parallel to a drive motor and a secondary battery is connected in parallel to the fuel cell and the capacitor through a DC/DC converter, is known as a drive source of a fuel cell vehicle (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-59689 (pages 4 to 5 and FIG. 1)).
In the conventional power supply device for vehicles, during a power running operation of the motor, an output voltage of the secondary battery is set by the DC/DC converter such that the capacitor is discharged preferentially to the fuel cell and the secondary battery. Further, during a regenerative operation of the motor, an output voltage to the secondary battery is set by the DC/DC converter such that the capacitor is charged preferentially to the secondary battery.
Further, there is provided an electric vehicle in which drive power is supplied to a motor from a battery during a power running operation of the motor and a secondary battery is charged with regenerative power generated during a regenerative operation of the motor (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-353033 (page 7 and FIGS. 4 and 5)). In the electric vehicle, limit values of output and input currents of the battery are determined on the basis of the temperature and remaining charging capacity of the secondary battery. Further, as the limit values of the output and input currents of the secondary battery are set in such a manner, it is possible to prevent the deterioration of the secondary battery.
However, in the above-mentioned electric vehicle 1, as the output current of the secondary battery is limited, the output of the motor is also limited. Therefore, the travel performance of the electric vehicle is degraded. Further, as the input current of the secondary battery is limited, the current at the time of recovering the regenerative power of the motor into the secondary battery decreases. Therefore, the overall regenerative power of the motor cannot be recovered, and the recovery rate of the regenerative power decreases.
Further, to prevent the degradation of the travel performance of the electric vehicle and the decrease in the recovery rate of the regenerative power, it is considered that the capacity of the secondary battery is increased. In this case, however, the volume of the secondary battery increases, so that the mounting space thereof expands. Further, the cost of the secondary battery increases.